The present invention relates to a transverse axle automatic transmission and more particularly to an improvement in the lubrication system of the various gear mechanisms of a transverse axle automatic transmission.
Transverse axle automatic transmissions combining integrally therewith the drive wheel differential and gear assembly are commonly termed "automatic transaxles"; therefore, that term will be used in the following description. In this type of transmission, the transmission chamber and final gear chamber are disposed adjacent each other, the transmission oil pan being positioned below the transmission chamber. The final gear chamber should store oil for lubricating the final gear assembly and the oil pan should store oil for lubricating the change-speed control mechanism and those portions of the power train within the transmission chamber requiring lubrication. A ring gear splashes oil from the final gear chamber upwards for lubricating the final gear assembly, while the oil pump withdraws oil from the oil pan via an oil intake port for lubricating the automatic change-speed control mechanism and the power train.
Automatic transaxles having the final gear chamber separated and independent of the oil pan are limited to full sized vehicles, due to the increased overall length inherent in this particular construction. For this reason, it is preferrable that the final gear chamber communicates with the oil pan so that common oil is used for lubricating the final gear assembly and for actuating and lubricating the automatic change-speed control mechanism and the power train.
Therefore, prior art devices have incorporated a connecting passage between the oil pan and final gear chamber. This passage is positioned as low as possible to most effectively permit transmission oil to freely flow therebetween. With this arrangement, if the oil level within the final gear chamber increases, an increased amount of oil is returned to the oil pan; an increase in oil level within the oil pan causes an increase in the amount of oil to flow through the connecting passage from the oil pan to the final gear chamber, causing an increase in the oil within the final gear chamber. Repeating this cycle results in a balanced in oil level in the final gear chamber and the oil pan. The initial objective is accomplished accordingly.
However, with the transaxle case of this construction, an excessive amount of oil in the oil pan will flow via said connecting passage into the final gear chamber, causing an oil shortage in the oil pan. This shortage is most serious when the level dips below the intake port, as when vehicle motion shifts and inclines the oil level therein. When this occurs, the oil pump sucks air rather than oil, causing a reduction in line pressure of the automatic change-speed control mechanism, causing such inconveniences as, excessive wear of the frictional elements, insufficient lubrication of the power train and racing of the engine, not to mention loss of power to the drive wheels.
In order to solve this problem, a baffle plate is positioned opposite the oil pan connecting port to minimize the effect of oil shifting. However, this measure is effective only against oil level shifts of a short time duration, therefore practically totally ineffective.